There is a very vocal guy in my gun club that has been saying for years. "They won't be able to stop all the guns, it's never going to be about the guns, IT'S ABOUT THE AMMO!"
The only ammo he buys is .22. He reloads everything else, and he has thousands of rounds of every caliber he shoots. For the slower speed ammo he casts his own bullets, for the speedier stuff he buys 10,000 bullets at a time. He has ample supplies of brass, primers, powder, bullets, and lead ingots for metallic, for shotgun he has hulls, primers, powder, wads, and shot in all of his standard sizes.
He is the guy that got me started reloading a few years ago, now the only ammo I buy is .22. I keep my chambering's simple making sure that I have several firearms in only a few standard calibers, and for shotgun I keep it to 12 gauge, but I am open to adding 20 gauge in the future.
Buy a couple of good presses and the components and get to work!
Ammunition is not mentioned in the Second Amendment, heck we have enough trouble with firearms, and they are mentioned.